CCTV footage has been released of a man police want to speak after a rail worker was threatened in Gloucestershire.
It happened on a train between Gloucester and Cheltenham Spa stations, shortly after 0600 BST on 10 September.
The guard was checking tickets when he came across a man who had no ticket and no means of paying.
He refused to give the guard his personal details and threatened him, using abusive language.
Pc Alan Fishpool, of the British Transport Police (BTP), said: "Although no violence was used, the guard was left shaken by the incident and feared for his safety.
"After viewing CCTV footage from on board the train, we have identified a man we would like to speak to in connection with this incident and I would ask anyone who recognises him to contact police."
The man is described as black, about 6ft 2in tall and slim. He was wearing a yellow shirt with a grey sleeveless top and dark trousers.